UNIVERSITY   OF   CALIFORNIA 

COLLEGE    OF   AGRICULTURE 
AGRICULTURAL   EXPERIMENT  STATION 

CIRCULAR  No.  264 
May,  1923 

PRELIMINARY  ESSENTIALS  TO  BOVINE  TUBERCULOSIS 
CONTROL  IN  CALIFORNIA 

By  GEOEGE  H.  HAET 


Non-reacting  yearling  heifers,  the  offspring  of  tuberculous  sires  and  dams  in 
the  herd  shown  on  page  7.  Kept  free  from  tuberculosis  by  removal  at  birth 
to  a  separate  ranch  and  raised  on  properly  pasteurized  milk. 


INTEODUCTION 

During  the  past  few  years  the  state  of  California  has  rapidly 
advanced  to  national  prominence  in  the  dairy  industry  field.  In  this 
state  many  of  those  factors  essential  to  progressive  dairying,  such  as 
the  elimination  of  the  scrub  bull,  development  of  cow  testing  associa- 
tions, dairy  sanitation,  advanced  registry  work,  and  improved  quality 
of  dairy  products,  are  being  developed  along  constructive  lines  on  a 
large  scale.  These  progressive  measures  bring  into  strong  contrast  the 
indifference  which  often  exists  in  regard  to  the  health  of  the  dairy 
animals,  an  indifference  which  is  prevalent  despite  the  obvious  fact 
that  no  single  factor  in  progressive  dairying  is  more  fundamental  than 
the  health  of  the  herds  that  make  the  foundation  upon  which  the  entire 
industry  rests. 


Z  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

For  many  years  California  was  obliged  to  import  dairy  cattle. 
'  This  was  necessary  for  the  development  of  our  herds  to  their  present 
number,  size,  and  quality  in  the  comparatively  short  period  of  time 
in  which  it  has  been  accomplished.  High  producing  pure-bred  and 
grade  cattle  have  been  shipped  in  from  the  thickly  populated  dairy 
centers  in  the  Middle  West  and  the  Atlantic  Coast.  It  is  well  known  to 
all  persons  who  have  studied  the  history  and  distribution  of  tuber- 
culosis that  such  areas  are  the  most  heavily  infected  with  this  disease. 
At  the  time  this  importation  was  taking  place,  animals  that  gave  a 
negative  reaction  to  the  tuberculin  test  were  commonly  accepted 
without  any  investigation  as  to  the  history  of  tuberculosis  in  the  herds 
from  which  they  originated.  Although  the  importance  of  considering 
the  tuberculin  test  history  of  the  herd  rather  than  of  the  individual 
cow  was  recognized  at  the  time,  and  had  been  clearly  set  forth  by  the 
International  Commission  of  the  American  Veterinary  Medical  Asso- 
ciation on  the  Control  of  Bovine  Tuberculosis,  it  had  not  been  given 
specific  attention.  Even  today  it  is  still  far  from  being  given  universal 
consideration  in  the  purchase  of  tuberculosis-free  cattle. 

The  disease  was,  therefore,  brought  into  the  state  in  many  cases 
with  the  foundation  stock  that  started  a  certain  number  of  our  pure- 
bred herds.  In  a  few  instances,  in  animals  kept  under  the  most 
approved  conditions,  tuberculosis  was  found  to  be  present  so  soon  after 
their  arrival  that  there  could  be  no  question  that  it  had  been  brought 
in  with  them. 

On  account  of  the  long  distance  they  had  been  shipped,  their  cost 
per  head  upon  arrival,  the  difficulty  of  getting  financial  redress  from 
the  original  owners,  and  the  need  for  high-producing  dairy  animals  of 
proper  blood  lines  in  the  state,  the  owners  became  indifferent  to  the 
importance  and  seriousness  of  the  disease,  and  affected  animals  were 
allowed  to  remain  in  the  breeding  herds.  This  was  particularly 
unfortunate  because  from  these  herds  pn re-bred  sires,  and  often 
foundation  females,  went  out  to  the  grade  herds.  The  question  of 
tuberculosis  or  the  tuberculin  test  was  not  raised  at  sales  within  the 
state  for  years.  The  spread  of  the  disease  was  greatly  augmented  by 
transferring  cattle  in  small  groups  from  farm  to  farm  by  means  of 
the  public  auction.  Many  herds  of  badly  diseased  cattle  were  thus 
distributed  throughout  the  state. 

Since  1915,  when  the  state  pure  milk  law  was  passed  requiring 
tuberculin  testing  of  cows  whose  milk  was  to  be  consumed  in  the  raw 
state,  the  demand  for  tuberculin  tested  cattle  has  been  gradually 
increased.    To  meet  this  demand  it  has  been  the  practice  to  purchase 


Circular  264]      BOVINE  TUBERCULOSIS  CONTROL  IN  CALIFORNIA  3 

animals  subject  to  the  test.  However,  the  seller  has  frequently  kept 
the  reactors  in  his  own  herd  or  sold  them  later  to  a  buyer  not  demand- 
ing a  tuberculin  test  certificate. 

Years  of  such  practices  are  now  having  their  effect.  Tuberculosis 
is  a  chronic  and  slowly  progressing  disease  in  a  great  many  of  the 
individual  animals  attacked.  T  have  known  cows  to  remain  profitable 
dairy  animals  for  eight  years  after  they  first  reacted  to  the  tuberculin 
test.  It  is  not  a  disease  that  devastates  the  herd  in  a  short  time.  The 
losses  it  causes,  though  very  large  in  the  aggregate,  extend  over  so  long 
a  period  of  time  that  they  are  not  acutely  felt. 

Despite  the  presence  of  this  disease,  therefore,  our  dairy  herds  have 
increased  in  number  and  size  until  we  are  now  in  a  position  to  become 
a  dairy  cattle  exporting  state.  The  demand  for  export  cattle  is  present 
in  Mexico,  the  Rocky  Mountain  states,  particularly  Nevada,  and  the 
islands  and  countries  on  the  Pacific,  and  this  demand  will  undoubtedly 
increase.  We  have  the  cattle  and  their  dairy  quality  is  satisfactory, 
but  they  do  not  possess  the  necessary  health  qualifications.  In  several 
instances  animals  exported  from  this  state  have  not  satisfactorily 
passed  tuberculin  tests  upon  arrival  at  their  destinations.  Today  the 
elimination  of  affected  animals  from  interstate  and  foreign  shipment 
is  looked  after  very  carefully  by  purchasers  as  well  as  livestock 
sanitary  authorities.  Even  though  California  is  the  logical  source 
of  supply  for  export  animals  to  the  above-mentioned  points,  there  is 
no  possibility  of  this  market  being  maintained  unless  our  cattle  can 
meet  the  health  requirements.  At  the  same  time,  the  local  demand 
for  tuberculosis  free  cattle  is  greater  than  the  supply,  which  condition 
is  forcing  purchases  of  such  animals  from  outside  the  state  and  further 
interfering  with  the  home  market. 

The  accredited  herd  and  tuberculosis-free  area  work  being  carried 
out  on  a  large  scale  by  the  Federal  Bureau  of  Animal  Industry  in 
cooperation  with  all  of  the  states,  has  developed  a  large  number  ot 
tuberculosis-free  herds  in  the  United  States.  This  work  has  been 
started  recently  in  this  state. 

Many  of  our  livestock  owners  are  getting  a  correct  idea  of  the 
situation  and  want  to  take  action,  while  others,  who  undoubtedly 
recognize  the  facts,  want  to  postpone  action  as  long  as  possible  in 
order  that  their  present  activities  in  the  sale  and  movement  of  cattle 
may  not  be  restricted.  The  well-informed  already  realize,  and  the 
majority  of  our  dairy  cattle  owners  must  appreciate  the  fact,  that 
there  are  very  important  preliminary  essentials  to  be  considered  in  a 
matter  of  this  kind. 


4  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

Much  discussion  has  ensued  regarding  the  value  of  the  tuberculin 
test,  which  of  the  three  tests  is  preferable,  how  the  reading  of  the  test 
shall  be  made,  whether  animals  once  reacting  and  later  failing  to  do 
so  should  be  considered  healthy,  and  many  other  points,  to  the  entire 
exclusion  of  the  following  essential  considerations: 

THE  DEVELOPMENT  OF  A  SOURCE  OF  SUPPLY  OF  FEMALES  OF 
EQUAL  QUALITY  TO  REPLACE  THE  REACTING  ANIMALS 

This  is  one  of  the  most  difficult  problems  that  presents  itself  in  a 
widespread  campaign  for  controlling  tuberculosis.  Many  owners  of 
livestock  would  be  willing  to  have  the  tuberculin  test  applied  and  stand 
the  loss  in  disposing  of  the  reacting  animals,  provided  they  could 
purchase  healthy  animals  to  take  their  places.  Many  years  ago  it 
was  found  impossible  to  purchase  cattle  free  from  tuberculosis  for  the 
certified  dairies  around  San  Francisco  Bay  on  the  tuberculin  test 
alone.  The  Medical  Milk  Commissions  of  San  Francisco  and  Alameda 
counties,  therefore,  adopted  in  1909  what  has  been  termed  the  ' '  10  per 
cent  rule"  for  all  purchases.  This  consists  in  having  all  the  animals 
in  a  herd  from  which  purchases  are  to  be  made  tested  with  tuberculin, 
and  in  case  more  than  10  per  cent  react  the  entire  herd  is  to  be 
rejected.  The  purchase  of  cattle  under  these  restrictions  became  so 
difficult  on  account  of  the  prevalence  of  the  disease  that  all  of  the 
certified  dairies  are  now  keeping  up  the  numerical  strength  of  their 
herds  to  a  large  extent  by  raising  young  stock  on  their  own  premises. 

At  the  present  time,  many  carloads  of  grade  cattle  are  being 
shipped  into  the  Los  Angeles  district  annually  from  the  Middle  West 
because  the  San  Joaquin  Valley  and  other  points  in  the  state  from 
which  these  animals  should  be  supplied  cannot  meet  the  health  test. 
While  tuberculosis-free  cattle  can  be  supplied  from  outside  the  state, 
the  distance  of  shipping,  time  required  for  acclimation,  and  the  cost 
are  prohibitive  to  a  considerable  percentage  of  our  dairy  herd  owners. 

The  tuberculosis-free  area  work  carried  on  in  remote  places,  such 
as  Lassen  and  Modoc  counties  and  in  Round  Valley  in  Mendocino 
County,  is  being  undertaken  because  in  these  places  there  are  small 
numbers  of  dairy  animals  many  of  which  are  native  stock  and  have 
not,  therefore,  become  heavily  infected  with  this  disease.  Such  areas 
at  the  present  time,  although  comparatively  free  from  tuberculosis, 
furnish  no  source  of  supply  of  healthy  females.  It  is  possible,  how- 
ever, for  females  to  be  raised  in  these  areas  even  though  they  have 
to  be  shipped  from  the  dairy  districts  as  weaned  calves  and  regularly 
tuberculin  tested.    In  time  such  free  areas  may  devote  their  attention 


CIRCULAR  264]     BOVINE  TUBERCULOSIS  CONTROL  IN  CALIFORNIA  5 

to  the  raising  of  dairy  rather  than  beef  animals  because  greater 
financial  returns  will  be  obtained  thereby.  Livestock  men  should 
seriously  consider  this  phase  of  the  tuberculosis  problem  and  cooperate 
to  solve  it. 

THE  IMPORTANCE  OF  HERD  TUBERCULIN  TESTS  RATHER  THAN 
TESTS  UPON  INDIVIDUAL  ANIMALS 

It  is  essential  for  livestock  men  to  understand  at  the  outset  that 
the  tuberculin  test  is  not  100  per  cent  efficient.  The  test  furnishes, 
however,  an  entirely  satisfactory  means  of  controlling  tuberculosis  if 


Fig.  1. — This  cow,  apparently  in  perfect  health,  was  found  to  be  tuberculous 
on  application  of  the  tuberculin  test. 

its  limitations  are  recognized  and  proper  consideration  given  them. 
A  single  animal  that  gives  a  negative  tuberculin  test  may  or  may  not 
be  tuberculous,  but  a  herd  of  animals  kept  together  for  a  reasonable 
period  of  time  all  giving  a  negative  tuberculin  test  may  safely  be 
considered  free  from  the  disease.  In  herds  where  there  are  certain 
percentages  of  reactors  we  can  expect  to  get  rid  of  the  disease  by 
removing  the  reactors,  subject  to  certain  conditions.  Except  in  special 
cases,  all  the  animals  in  herds  that  are  running  from  35  per  cent  to 
50  per  cent  or  more  reactors  should  be  considered  diseased.  In  general 
the  larger  the  herd  of  animals,  the  lower  must  be  the  percentage  of 
reactors  if  the  herd  is  ever  to  become  entirely  free  from  the  disease. 


6  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

For  example,  in  a  small  herd  of  twenty  cows,  five  or  six  may  react 
and  by  removing  these  animals  the  disease  may  be  eliminated  from 
the  herd  with  one  or  more  subsequent  tests.  In  case,  however,  there 
were  two  hundred  animals  and  the  same  percentage  of  reactors  was 
found,  the  opportunity  for  eradicating  the  disease  from  that  herd  would 
be  much  more  difficult;  and  were  the  herd  to  consist  of  a  thousand 
animals  the  difficulties  would  become  many  times  greater.  The  reason 
for  this  is  that  the  larger  the  herd,  the  greater  the  number  of  tuber- 
culous animals  present,  even  though  the  percentage  is  no  greater  than 
in  smaller  herds.  The  more  animals  actually  affected  with  the  disease 
in  a  herd,  the  greater  the  opportunity  for  one  or  more  to  fail  to  react 
to  the  test.  These  non-reactors  are,  therefore,  left  in  the  herd  and 
continue  to  spread  the  infection  through  discharges  from  their  bodies. 
For  this  reason  it  is  less  costly  to  take  out  several  animals  that  may 
show  no  lesions  on  postmortem  examination  than  to  leave  one  affected 
animal  in  the  herd.  Although  it  is  difficult  for  the  livestock  man  to 
accept  the  fact  that  whole  herds  of  cattle  may  be  tuberculous  and  that 
the  control  of  the  disease  should  be  started  from  this  basis  in  certain 
herds,  the  sooner  it  is  recognized  the  more  certainly  will  time  and 
money  be  saved  and  endless  discouragement  avoided.  The  decision  in 
matters  of  this  kind  will  require  careful  thought  and  consideration  by 
the  owner  and  the  advising  veterinarian. 

BRANDING  OF  EEACTING  ANIMALS 

At  the  present  time  a  great  many  owners  of  livestock,  who  believe 
that  they  are  ready  for  the  tuberculosis  eradication  campaign  to 
progress  rapidly  in  this  state,  are  considerably  taken  aback  when  it  is 
stated  that  they  must  allow  all  reacting  animals  to  be  branded  with 
the  letter  "T."  This  is  an  absolutely  essential  procedure  for  the 
control  of  the  disease  and  must  be  rigidly  enforced  upon  all  veter- 
inarians who  apply  tuberculin  tests,  whether  official  or  private.  Under 
the  present  system  that  exists  in  this  state,  it  is  not  uncommon  for 
persons  to  buy  cattle  and  have  them  tested  by  their  own  veterinarians. 
Only  the  non-reactors  are  taken.  A  short  time  after,  another  purchaser 
may  appear  with  his  veterinarian  and  test  the  herd,  again  taking  the 
non-re  ictors.  Nothing  is  done  with  the  reactors  and  no  method  of 
identification  is  placed  upon  them.  It  is  a  well  known  fact  that  an 
animal  which  once  reacts  to  the  tuberculin  test  may  not  react  to  one 
or  more  subsequent  tests,  and  particularly  is  this  the  case  when  subse- 
quent tests  are  applied  in  rapid  succession.  Therefore,  under  such 
conditions  all  of  the  animals  may  be  sold  as  non-reactors,  although 


CIRCULAR  264]      BOVINE  TUBERCULOSIS  CONTROL  IN  CALIFORNIA  7 

they  may  have  reacted  to  several  tests  previous  to  the  one  on  which 
they  were  purchased  when  they  did  not  react.  Such  a  procedure 
carried  out  generally  will  make  it  impossible  for  any  conscientious 
private  veterinarian  to  do  any  tuberculin  testing,  because  he  will  be 
confronted  with  conditions  entirely  beyond  his  control  which  com- 
pletely vitiate  the  value  of  his  work,  but  for  which  he  will  receive  the 
responsibility  and  condemnation. 

Where  tuberculous  animals  are  properly  branded  and  segregated 
they  may  under  special  conditions  remain  profitable  cows  for  a  period 
of  years  during  which  time  they  can  annually  produce  healthy  off- 
spring of  the  quality  that  is  desired  to  keep  production  at  its  normal 


Fig.   2. — This   herd   of   cattle   gave    67   per   cent   positive   reactions   to   the 
tuberculin  test.     The  entire  herd  was,  therefore,  considered  tuberculous. 

level  during  the  eradicaton  work.  A  test  and  slaughter  campaign 
in  this  state  carried  out  too  rapidly  would  materally  reduce  produc- 
tion and  interfere  with  the  prosperity  of  the  dairy  industry.  Where 
segregation  is  attempted  it  must  be  thorough  and  complete,  with 
separate  land  and  buildings.  Only  a  small  percentage  of  dairy  cattle 
owners  are  equipped  to  carry  out  such  a  plan  and  in  general  they  are 
those  having  large  herds  and  acreage  and  particularly  those  having 
two  or  more  ranches. 


CONTEOL  OF  TUBEECULIN 
The  control  of  tuberculin  is  also  of  great  importance  as  a  pre- 
liminary essential  for  controlling  tuberculosis.     Under  present  con- 
ditions anyone  can  purchase  tuberculin  and  frequently  one  has  to  go 
no  farther  than  the  town  drugstore  to  get  a  supply.    Large  quantities 


8  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT   STATION 

of  it  axe  being  used  by  persons  who  are  entirely  unqualified  to 
administer  it  but  who  intend  to  use  it  honestly  to  the  best  of  their 
ability.     Other  persons  are  using  it  with  fraudulent  intentions. 

I  recently  visited  a  dairy  ranch  operated  by  a  progressive  dairy- 
man. He  was  having  his  herd  regularly  tested  by  an  official  veter- 
inarian under  the  state  pure  milk  law  on  account  of  his  product  being 
sold  as  raw  milk.  He  told  me  that  he  always  kept  a  supply  of 
tuberculin  on  hand  and  whenever  a  cow  looked  out  of  condition  he 
tested  her  himself.  Such  indiscriminate  testing  is  of  no  value  and 
only  tends  to  reduce  the  efficiency  of  the  testing  done  by  the  official 
veterinarian. 

In  many  of  the  states  of  the  Union,  including  those  where  the  tuber- 
culosis campaign  is  progressing  most  satisfactorily,  tuberculin  is  under 
the  absolute  control  of  the  State  Livestock  Sanitary  authorities.  All 
shipments  of  this  material  into  the  state  and  all  sales  of  same  by 
laboratories  within  the  state  must  be  recorded  with  the  State  Veter- 
inarian. In  case  reports  of  the  use  of  tuberculin  are  not  received  or 
there  is  a  question  as  to  the  honesty  or  ability  of  the  persons  using  the 
material,  that  fact  is  at  once  investigated  by  the  authorities.  This 
gives  opportunity  for  the  control  of  this  material  so  that  fraudulent 
practice  is  carried  on,  if  at  all,  with  great  difficulty. 

"We  believe  that  the  testing  by  livestock  owners  of  their  own  and 
their  neighbors'  herds  of  cattle  must  be  stopped  through  control  of 
tuberculin.  These  tests  are  not  recognized  by  purchasers  of  the 
animals  and  from  the  results  that  have  been  obtained  both  in  this  and 
in  other  states  it  is  plainly  evident  to  the  thinking  man  that  such 
practice  will  never  be  successful  in  controlling  this  infection  of  live- 
stock. As  long  as  it  is  allowed  to  continue,  control  of  reactors  is 
impossible.  A  majority  sentiment  of  our  livestock  men  must  be 
developed  to  back  morally  and  legally  any  movement  to- bring  about- 
the  complete  suppression  of  this  type  of  work. 

With  these  primary  necessities  properly  understood  and  statutes 
developed  to  render  their  application  possible,  we  are  then  ready  to 
proceed  wth  tuberculosis  eradication  work  on  a  reasonable  scale. 
Many  of  the  lesser  points,  such  as  the  handling  of  cattle  at  fairs,  the 
proper  disinfection  of  railway  cars  and  stockyards,  the  question  of 
indemnity  and  disposal  of  reacting  cattle  through  slaughter  houses  to 
the  best  financial  advantage  of  the  owner,  and  so  forth,  are  matters 
which  will  develop  as  the  work  progresses. 


